1. Field of the Invention
The invention relates to fire doors. More particularly, the invention relates to a fire door stop to stop the spread of smoke, hot gases, or fire from flowing between a fire door and the door frame.
2. Discussion of the Prior Art
The National Fire Protection Association (NFPA) develops codes and standards that minimize the risk and effects of fire and other hazardous situations. NFPA 80 regulates the installation and maintenance of assemblies and devices used to protect openings in walls, floors, and ceilings and as of 2007 requires that all doors and door frames that are labeled fire doors and labeled fire door frames be inspected and tested annually. This standard is herein incorporated in its entirety by reference. NFPA 80 specifies the allowable clearances or gaps between fire door and frame and the floor. Currently, the specified clearance between door and frame is ⅛ inch, plus or minus 1/16 inch, for steel doors, and shall not exceed ⅛ inch for wood doors. The clearance between the bottom of the fire door and the floor shall be a maximum of ¾ inch.
Precise standards regulating fire doors exist to ensure that a fire door assembly, which includes a fire door and a fire door frame with door frame, functions as desired to stop the flow of fire, hot gases, and smoke. The standards require that the fire door assembly, i.e., the labeled door frame and the labeled fire door, be built to a specified size and then be installed, such that about ½ inch of the edge of the door overlaps the soffit height of the frame, which is typically ⅝ inch deep, thereby creating an overlap interface between fire door and door frame. The specified clearance between door and frame is ⅛ inch, plus/minus 1/16 inch for steel doors, and shall not exceed ⅛ inch for wood doors. Clearances are always measured from the pull face of the door. This overlap is necessary in a fire condition to keep the fire door in place and together, when a fire hose water stream is put onto the fire door, and to hold back the fire, hot gases, and smoke, and also to allow for shrinkage in wood doors, as the wood edges burn away in a fire condition.
Unfortunately, the doors and door frames are built to the minimum standards and, if the installation isn't perfect, the clearance between the edge of the labeled fire door and the labeled door frame may be excessive, such that the overlap is less than specified or that a gap exists between the edge of the door and the edge of the frame. There are an estimated 150 million fire doors installed in the US today and 80% of them fail a first-time inspection. The overwhelming majority of the failures are due to excessive clearance between door and door frame. Typically, the excessive clearance is ¼ to 5/16 inch wide, with some clearances as large as ½ inch.
Also, buildings settle over the years, increasing imperfections in the installation and contributing to the formation of an excessive clearance. The remedy is to shim the door frame to eliminate the excessive clearance, or to replace the door and frame altogether. Replacing the door and/or frame is not only costly, but may be nearly impossible. In many commercial building, including hospitals and schools, the fire door frames are embedded in concrete as the building is constructed. Even the less invasive remedy of shimming the door frame can be impossible in this case. If it is possible to shim the door, this means pulling the door from the hinge side toward the lock side, which then frequently creates an excessive clearance on the hinge side.
What is needed, therefore, is a simple, reliable means of eliminating a gap between a labeled fire door and labeled fire door frame, even when both door and frame have been built to minimum standards.